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Hitting the wall

By Chris Madson, on January 18th, 2011

Some thoughts

on the occasion

of the 2010 Census

On April 14, 1996, biologists with the National Park Service opened the gate of a pen on Rose Creek, a small tributary of the Lamar River in the northeastern corner of Yellowstone National Park. The five wolves inside had waited two months for the moment. They had been trapped in northern British Columbia and flown to Yellowstone that January, an adult female and her three pups from one pack and a dominant male from another pack nearby. After two months of confinement, they stepped through the gate and became the most famous wolves in the history of their species— the Druid Peak pack.

At the time, northern Yellowstone supported more than 17,000 elk and 500 bison, none of whom had ever seen a wild dog larger than a coyote. Part of the world’s first national park, it afforded complete protection from trappers and other humans, and on the day the gate opened, there were only twenty-six other wolves in the country. For the five new immigrants, it must have seemed like Eden.

They staked out a territory of 300 square miles, much of it in the sagebrush prairie on either side of the Lamar, where their activities could be easily watched and filmed. Wolf groupies gathered along the highway by the hundreds with Leica binoculars and Questar spotting scopes in hand, while filmmakers captured most of the pack’s daily affairs for documentaries on public television and the BBC.

By 1999, there were 118 wolves in Yellowstone and eight in the Druid pack. It was in that year that biologists saw the first signs of trouble in paradise. Only two of the Druid’s six pups survived the summer and only thirty-eight of sixty-four pups in the park lived to see the end of the year. Subsequent blood tests suggested that most of the pups had died of canine distemper, a disease they probably picked up from other wild animals in the park. The blood analysis showed that the wolves had also been exposed to parvovirus and hepatitis.

Nor was disease the only killer. Two wolves in the Soda Butte pack, a neighbor of the Druids, were killed by other wolves. The following year, the Druid’s dominant female was killed by other members of the pack, probably the two subordinate females she had ruthlessly disciplined for two years.

By 2002, there were thirty-seven animals in the Druid pack, many of which left during the spring to form three new packs, which inflicted casualties on each other and the Druids as they competed for control of the Lamar valley. Three more adult wolves died in fights for territory. In 2003, five more were killed in territorial struggles; in 2004, at least four more; in 2005, eight more.

Another round of canine distemper swept the wolf dens in 2005— only twenty-two of sixty-nine pups whelped in the park survived. All the pups produced by the Druid pack died. At the same time, mange appeared among the wolves. Mange is caused by a small mite that nibbles on the skin of its host, then feeds on the fluids that ooze from the tiny wounds. As the mites multiply, the inflammation causes the infected animal to shed patches of skin and hair. A case of mange isn’t fatal by itself, but it deprives an infected wolf of the fur it needs to withstand sub-zero temperatures during the winter. The increased energy demand is often more than the wolf can sustain. At least three wolves died of the effects of manage in 2005.

The Yellowstone wolves killed four more of their number in 2006, four in 2007, and ten in 2008. The Druids numbered thirteen that year, but only five of their eighteen pups survived to year’s end, probably because of another outbreak of distemper, and the pack members that remained were hard-pressed by mange and competition from surrounding packs.

Last March, Doug Smith, Yellowstone’s wolf biologist, announced that the Druid pack was probably on its way out. “They’re down to one,” he observed, “and that one probably won’t make it through the winter.” When last seen, she was suffering from a severe case of mange and was likely to die a lingering death from exposure and starvation. So much for the world’s most famous wolves.

By the numbers

In the natural world, this is how populations are controlled. At the beginning when a small group of animals finds its way into new country, the pioneers have to learn the landscape and the opportunities it offers, a process that can take several generations, during which the population grows slowly as individuals struggle to learn the ropes.

With luck, members of the population eventually hone their ability to exploit their environment. In some species, this may be learned; in others, it may be the result of natural selection. Either way, these generations are set to succeed. Better fed, better sheltered than their predecessors, they produce more young and manage to get more of their infants to adulthood. At the same time, adults tend to live longer. The result is a drastic increase in the rate at which the population grows.

A population in this phase of its growth may take some interesting evolutionary paths. If an individual isn’t limited by food, it can afford to spend more of its time and energy on specialized behaviors and structures. Competition for mates is often more important than competition for resources in these populations. All this can easily lead to a heavy investment in the rituals that surround sex— males may get larger and more powerful; they may develop outlandish symbols of their virility like the antlers of a seven-point bull elk or the specialized plumage and air sacs of a sage grouse cock; they may invest in intense courtship displays.

An evolutionary biologist would caution against making any value judgments about such developments; from a strictly evolutionary point of view, they are simply ways to ensure survival of certain associations of genes. But it’s hard to look at any wild population in this maximum growth phase and not reach the conclusion that life is exceptionally good for animals that have found a way to succeed but haven’t yet run into shortages of food or cover. The chances are good that each individual will live a long, healthy life with plenty of food, plenty of room, appealing mates, and many thriving offspring. Does it get any better than that?

It is one of the tragedies of life on earth that all resources are finite. Sooner or later, a growing population begins to encounter shortages, spotty at first, more pervasive and longer-lasting as time goes on and numbers grow. Different animals have different ways of responding to growing numbers of their own kind. When there are too many elk on Yellowstone’s north range, the herd damages the plants it depends on for food. Less food means more starving elk; more starving elk leads to greater winter losses and fewer newborn elk— eventually, the population falls.

Wolves may run into the same fundamental limits when it comes to food, but often, their increasing numbers cause trouble in their social order before a lack of food comes to bear. Issues of territory and dominance typically begin to constrain their population growth before the game runs out. This strife may not be pretty, but it insulates the wolves from the local extinction that would occur if their numbers overshot their prey and they killed the very last game animal.

Of course, predators also take a hand in the control of any population of animals. We think of predators in terms of tooth and claw, but they aren’t always powerful and ferocious. Some are single-celled creatures that stalk their prey through alternate hosts and prefer to do their feeding inside their victims. Large predators like grizzlies and small predators like distemper viruses share few outward traits, but they tend to react in the same way to a change in a prey population. When a given species of prey is rare, predators and diseases have trouble finding victims; as the population density of potential prey increases, losses to both predators and disease are likely to increase. That rule applies to wolves as surely as it does to rabbits.

From the point of view of an overall population, I suppose success can be measured strictly by the numbers— the closer a population comes to filling its niche and fully exploiting its resources, the more successful it is. But a look at life in the Druid pack over the last decade suggests that an individual’s life isn’t all that enjoyable as the population hits the wall. Life spans tend to be shorter. Females bear fewer young, and fewer of those young survive their infancy. Disease is more common, both because animals are in poorer shape and because communicable diseases spread more easily in dense populations than in sparse ones. Violent behavior between members of the same species increases.

It’s interesting that one of Yellowstone’s annual reports on the Druid pack mentions, in passing, that “compared to other wolf pups in Yellowstone, the Druid pups were slightly smaller.” There are several possible explanations for the disparity: It may have been a temporary variation or a statistical anomaly; it may have been due to the large number of pups the Druid pack whelped that year. It could also have been a reflection of growing population stresses in the pack, stresses that reached even into the nursery.

Fill ’er up

Radio host Michele Norris had just finished her segment on the demise of the Druid pack when my wife bustled into the kitchen and thumb-tacked an official-looking form on the bulletin board, her way of suggesting that I ought not forget it. I took a closer look— it was from the U.S. Census Bureau. Well, I thought to myself, on the scale of federal forms, this one’s not so tough. And I’m happy to do my part in the pursuit of an accurate national nose count, curious— and more than a little apprehensive— about what the 2010 census will show.

The growth of America’s population is as much a matter of myth as fact. No one knows whether Daniel Boone ever said that he was moving west to find “more elbow room,” but an Englishman who traveled the American frontier in 1796 and 1797 did record this conversation with the backwoodsman:

“He said he had a great deal of land given him on the first settlement of the country; but that when societies began to form around him, he moved off, and divided his land among his relations, unwilling (as he expressed himself) to live among men who were shackled in their habits, and would not enjoy uncontrolled the free blessings which nature had bestowed upon them. Since this time, he told me he had spent his time a great deal on the frontiers; and at this present moment he said he was going to hunt for beavers in some unfrequented corner of the woods, where undisturbed he might pursue this amusement, and enjoy the pleasures arising from a secluded and solitary life.”

The pattern of Boone’s life— the move from Pennsylvania to North Carolina, from Carolina to Kentucky, from Kentucky to Missouri— reflected the habits and preferences of an entire class of Americans. They were a people who remembered what it was like to scratch a living from ten acres of farmland that belonged to another man. Many of them were fresh from the harsh realities of a Europe that was increasingly crowded, a place that was controlled by a landed class that passed the privileges of rank from one aristocratic generation to the next.

The American frontier was fraught with a unique set of dangers, but for all the risk, it offered free land, free water and timber, free fish and game. The advantages were not lost on emigrants from the Old World. Wave after wave of them took the measure of the new continent and agreed with one of Boston’s earliest residents, Thomas Morton, who wrote that “the more I looked the more I liked it. And when I had seriously considered the beauty of the place, with all her fair endowments, I did not think that in all the known world it could be paralleled.”

Unfortunately, the frontier lifestyle carried the seeds of its own destruction. When the first U.S. census was taken in 1790, the nation’s population stood at 3,929,214. In the next decade, it increased by thirty-five percent and by another thirty-six percent the decade after that. As the march toward Manifest Destiny picked up speed, some observers were ambivalent about it. John C. Calhoun, a Congressman from South Carolina who later became vice president of the United States, commented on the growing risk that the nation would split into smaller countries. “We are greatly and rapidly— I was about to say fearfully— growing,” he said in an address to the House of Representatives in 1817. “This is our pride and our danger; our weakness and our strength.”

By 1870, American population had increased by a factor of ten, and in 1890, the superintendent of the Census Bureau, Robert Porter, noted an unprecedented change in the nation’s demographic affairs:

“Up to and including 1880 the country had a frontier of settlement, but at present the unsettled area has been so broken into by isolated bodies of settlement that there can hardly be said to be a frontier line. In the discussion of its extent, its westward movement, etc., it can not, therefore, any longer have a place in the census reports.”

The American frontier had vanished.

Historians have debated the importance of this milestone in national development ever since Frederick Jackson Turner first commented on it in 1892, but regardless of its effect on the American character, it had no effect on the growth of American population. In 1915, U.S. population passed 100 million, three centuries after the first English-speaking colony was established at Jamestown. We reached our second hundred million in 1968, fifty-three years later. We added our third hundred million in 2007, thirty-nine years after that. The specialists estimate that we’ll add our fourth hundred million by 2039, thirty-two years after the third.

Some observers of this trend are buoyantly optimistic about having another hundred million people in the United States, believing that a youthful, growing population will give us a powerful competitive edge in an aging world. It’s an appealing fantasy, based on a child-like faith in the past. As Denver columnist and talk-show host Mike Rosen puts it: “I’ll cast my fate with freedom, human ingenuity and revolutionary technologies creating new resources, as has been the case throughout history.”

We’ll see how “human ingenuity and revolutionary technologies” help us with 100 million new bodies in the next thirty years. We’ll need something like 10 billion more gallons of water each day, and that’s assuming every new user applies the kind of conservation measures that Tucson, Arizona, has adopted to cope with water shortages. At current levels of consumption, those new Americans will need 260 million more gallons of petroleum a year, 75 trillion more cubic feet of natural gas, and a trillion kilowatt-hours of new electricity. They’ll need 3 billion more bushels of corn a year, 500 million more bushels of soybeans, and another 500 million bushels of wheat.

If Joel Kotkin, author of The Next Hundred Million, is right, about 60 million of these new Americans will settle outside of major cities in suburbs or exurbs. At 2.57 people per household, that will be about 23 million new houses on something like 10 million acres of land. Unless we radically change the way we build houses, that will take about 368 billion board-feet of lumber.

I have little doubt that we’ll do a better job of conserving resources in the next thirty years than we do now— we’ll have little choice. And Rosen may be right; some wunderkind in one of our universities may come up with a new battery that helps us build a better electric car. Still, there will be 100 million more Americans on the highway, at the mall, looking for a place to park, a place to stand, a place to be alone. We will be less free than we have been for the simple reason that one man’s freedom ends where another’s begins.

It’s fashionable in some circles to sneer at the predictions of population disasters that Thomas Malthus made 200 years ago, that Paul Erlich famously repeated in The Population Bomb in the 1960s. It’s easy to sneer when you’re living in the richest country in the world, with a population density that is eight percent of India’s and thirteen percent of Great Britain’s. If we had lived the last forty years in Somalia, Sudan, the Congo, Haiti, or Bangladesh, we might see the Malthusian warnings in a different light, but I’ll concede the point that an apocalyptic population crash may not be in our immediate future.

What seems to be happening is more subtle. Many societies seem to be feeling the crush of their numbers almost instinctively and reacting to it. In Europe, where human density has passed 600 people per square mile, demographers are predicting a significant decline in population over the next century. The economic reasons for this trend are clear to anyone who lives in a first-world country— these days, it takes longer for young adults to educate themselves and get into the workforce, and the cost of bearing and raising children continues to increase. Some observers argue that these market forces are having similar effects in China, even that the stabilizing Chinese population has more to do with the market than with their infamous one-child policy.

The advocates of infinite growth express relief that America is bucking the downward population trend in these countries. As Kotkin puts it: “Because of America’s unique demographic trajectory among advanced countries, it should emerge by mid-century as the most affluent, culturally rich, and successful nation in human history.” I guess we’ll see which view of 400 million Americans turns out to be more accurate— the economist’s or the ecologist’s.

Learning by example

In the short term, at least, the question isn’t whether we’ll live; it’s how well we’ll live. Many animal populations survive indefinitely in the gray world just short of collapse, but it’s not a comfortable existence. Yellowstone’s wolves have come to that uncomfortable place. The passing of the Druid pack is not a sign that wolves will disappear from Yellowstone anytime soon— there are already wolves vying to claim the territory the Druids left vacant. It is a sign that the Yellowstone wolves are approaching the limits of that environment, if they haven’t passed it already. The population will persist, but life for individual wolves will continue to be what it was for the Druids, an uphill struggle against disease, starvation, social upheaval, and internecine violence.

The fate of the Druids is more than a metaphor; it’s a practical demonstration of the pressures that come to bear on a population when it approaches the limits of the resources that support it. We’re not wolves, but in spite of our technological prowess, we’ll bow to the same forces in the end. Even here in the empty quarter of the continent, we feel them already in the shortage of resources as mundane as fresh water and as ethereal as untrammeled open space.

Like the Druid wolves, we live in a finite world. Unlike the Druids, we can choose how we live. We can decide to set our own limits and live lives unconstrained by scarcity. Or we can continue to breed our way into a confrontation with the limits nature imposes on us, hurling ourselves against the wall like a pack of wolves, only to fall back, bruised, bloodied, and surprised by a reality we ought to have understood two centuries ago.